/Engine/Source/Runtime/Engine/Classes/EdGraph/EdGraphSchema.h
Check whether new nodes can be user-created (by dragging off pins etc.)
the response to making a new connection
virtual [FPinConnectionResponse](API\Runtime\Engine\EdGraph\FPinConnectionResponse) CanCreateNewNodes ( [UEdGraphPin](API\Runtime\Engine\EdGraph\UEdGraphPin) * InSourcePin ) const